Mechanical behaviour of black anodic films on 7175 aluminium alloy for space applications

Yann Goueffon (1) , Catherine Mabru (2) , Michel Labarrère (2) , Laurent Arurault (3) , Claire Tonon (4) , Pascale Guigue (1)

1 CNES - Centre National d'Etudes Spatiales - Direction Des Lanceurs.
2 ICA - Institut Clément Ader
3 CIRIMAT - Centre interuniversitaire de recherche et d'ingenierie des matériaux
4 Astrium [Toulouse]

Because of their low outgassing and their thermo-optical properties, black anodized aluminium parts are often used near optical instruments to manage thermal control in space applications. However, critical cases of flaking of the film were observed after simulated thermal ageing. To understand the mechanisms leading to flaking, the influence of the initial porosity of the film on its mechanical behaviour during and after the black anodizing process has been investigated. The decrease of limit tensile stress with the porosity, the coloring and the sealing combined to thermal stresses due to the difference of coefficient of thermal extension between film and substrate has been shown to cause crazing in particular conditions. For high initial porosity films, thermal cycling ageing has a detrimental influence on the adhesion measured by scratch testing. Numerical simulation has been used to simulate the combined effects of thermal stresses and film cracking on the stress field at the interface.

Mots clés: Black anodizing; Thin films; Crazing; Flaking

Domaines: Matériaux; Matériaux et structures en mécanique [physics.class-ph]

Yann Goueffon, Catherine Mabru, Michel Labarrère, Laurent Arurault, Claire Tonon, et al.. Mechanical behaviour of black anodic films on 7175 aluminium alloy for space applications. Metal Finishing, 2010, 108 (2), pp.22-27. ⟨10.1016/S0026-0576(10)80037-6⟩. ⟨hal-01852209⟩